The invention relates to a guide wire in accordance with the preamble to Claim 1.
The catheters used in medical practice are flexible tubes, particularly of plastic, which are hollow throughout and can be introduced into cavities and canals of the human or animal body and serve to effect treatment within the body cavity or the canal or to make the body cavity or the canal visible by fluoroscopic or endoscopic methods. For this purpose, the catheters are introduced into the lumen in question. A therapeutic or contrast liquid can then be injected through the hollow of the catheter or a light guide can be introduced for endoscopic photographs or treatment with laser beam. For the avoidance of traumas and to assure sufficient flexibility, the material of the catheter is relatively soft and therefore can withstand only slight mechanical stresses. Accordingly, it is not possible to use such catheters to reach into fine branchings of the canal system, for instance of the blood vessels. Neither the torsional stability nor the required fineness of the catheter is sufficient for this.
In order to solve this problem, so-called guide wires have been developed whose outside diameters are between about 0.5 and 2 mm. Helically wound springs are provided at least at the distal end of these guide wires, the springs closely surrounding the distal end region and being fastened to it extending over a certain length beyond same. These helical springs are very flexible and are carefully rounded on their outer surface; a securing wire which is laid within the spring and connected to it at both ends prevents the spring from pulling apart so that the helical turns of the spring material lie closely alongside of each other. This helical spring and the distal end of the guide wire are either linear or bent at an angle of up to 180.degree., radii of curvature of down to 1.5 mm being obtained.
In this way, there is obtained a relatively soft arch on the distal end of the guide wire the legs of which can apply themselves against the channel walls and thus assure elastic guidance of the tip of the guide wire upon its advance into the convoluted canal system without the wall of the canal being pierced by the tip of the guide wire in narrow curvatures. Upon a slight pulling back of the guide wire the helical spring extends and passes from a J-shaped configuration into a merely slightly arched configuration in which the distal end of the helical spring rests against a canal wall. This procedure takes place in the case of narrow branchings which the guide wire is to follow. Special guide wires are designed with torsional stability, as a result of which, for instance, vessel exits can be probed selectively. Because of the high flexibility of the helical spring, the distal end region of the guide wire which is surrounded by the helical spring is preferably tapered or in any event made thinner than the inside diameter of the helical spring. As a result of this, this end region of the guide wire can be slightly bent over, as a result of which the helical spring is, as a whole, imparted the bend necessary for its guidance task and creates a sufficiently large radius of curvature to prevent trauma. For the carrying out of the diagnostic or therapeutic measure within the region of the vasiform lumen, the catheter must then still be pushed over the guide wire and, due to the mechanical properties of the guide wire, its catheter tip can now be selectively positioned.
From Federal Republic of Germany OS No. 33 34 174 a sturdy guide wire of this type is known. It has the disadvantage that, after introduction of the catheter which is pushed over it, it must be removed and replaced by a coaxial catheter in order that a smaller vessel region can be probed or a stenosis passed. The catheter which is introduced in place of the guide wire, however, has only limited mechanical strength with respect to torsional stability and axial load-bearing capacity and it therefore lacks the decisive feature of steerability. Accordingly, it can neither be guided in branches nor pass narrow curvatures and, in particular, it is not possible to pass through stenoses with it. Furthermore, the catheter when introduced, and in particular the position of its mouth, cannot be observed on the fluorescent screen since it does not absorb x-rays.
Catheterlysis treatments by means of a therapeutic agent or laser are also difficult with the known combinations of strong guide wire and catheter because the progress of the treatment can be observed only with difficulty, since, as a result of the single catheter lumen present, the fibrinolytic or x-ray contrast agent must be applied alternately. In particular, the fibrinolytic, which is washed out of the catheter upon each introduction of contrast agent, no longer is active locoregionally in the sense of catheterlysis and thereby systematically subjects the entire organism to stress. In this way, the economy of the use of the fibrinolytic is reduced. Verification of the progress of the thrombolysis therefore naturally takes place in relatively large steps and therefore without sufficient visual control.
From Federal Republic of Germany OS No. 29 16 097 a catheter arrangement having a guide wire is known. In this case, the outer catheter serves as guide catheter for the inner catheter. The guidance character of the guide catheter is based therefore exclusively on its ability to impart external support to the thin and accordingly unstable catheter which is guided in its lumen. It is not possible to go into narrow lumens with this guide catheter, if only because of its necessarily large outside diameter. Its use, therefore, is limited to large-size vessels.
From Federal Republic of Germany AS No. 25 05 790 there is known a hollow puncture needle for use in vein catheter instruments. It is suitable exclusively for manipulations at the place of puncture while the possibility of manipulating the tip of the needle far from the point of puncture is not present.